A majority of the world's population likely will experience some reduction in hearing capacity or a balance disorder in their lifetime. Approximately 17 percent (36 million) of American adults report some degree of hearing loss, and about 2-3 out of every 1,000 children in the United States are born deaf or hard-of-hearing (statistics from the National Institute on Deafness and Other Communication Disorders (NIDCD)).
In both hearing and balance, mechanical stimuli are translated into neural signals by sensory hair cells, damage to which is responsible for many types of hearing loss and balance disorders. Mechanical damage by, for example, loud noises, bends cochlear hair cells to the point that the hair cell can no longer transduce signals to the auditory nerves. As mammalian hair cells do not regenerate naturally, permanent hearing loss can occur if hair cells are damaged. Aside from acoustic trauma, which is the predominant cause of hearing impairment, hearing loss also can be caused by hereditary syndromes, bacterial or viral infections, use of prescription drugs, and presbycusis (hearing loss associated with old age). Likewise, balance disorders, especially vestibular disorders, can be caused by infection, head injury, pharmaceutical use, and age.
The most common treatments for hearing loss involve hearing aids and cochlear implants. Approximately 188,000 people worldwide have received cochlear implants, which includes roughly 41,599 adults and 25,500 children in the United States (NIDCD statistics). Treatment options for balance disorders include balance retraining, anti-vertigo or anti-nausea medications, and vestibular rehabilitation therapy. Such therapies, however, likely will be required over extended periods of time if the disorder is progressive, and many therapies for balance disorders do not provide permanent relief from dizziness. Currently, there are no effective pharmaceutical treatments for disorders involving loss or damage of sensory hair cells in the ear.
Thus, there remains a need for agents which can ameliorate disorders associated with destruction or loss of sensory hair cells, such as hearing loss and balance disorders. This invention provides such an agent.